Rotary joint with a mechanical seal

A rotary joint comprising:

• a stator and a rotor, each having at least one fluid channel;
• a fluid transfer interface between the stator and the rotor, via which a fluid flows from the fluid channel in the stator into the fluid channel in the rotor, or vice versa, wherein the fluid transfer interface is sealed off using a mechanical seal, which comprises an abrasive sliding ring, and the sliding ring bears in an axial direction in an elastically biased manner against at least one mating ring and forms a seal face therewith;
• wherein an axial displacement detection device is provided, which is designed to detect, in the event of wear on the sliding ring, an associated axial displacement of the stator and/or rotor;
• wherein the axial displacement detection device comprises a rotary encoder on the rotor and a sensor that detects a position of the rotary encoder, said sensor being located radially opposite the rotary encoder, and the rotary encoder comprises at least one discrete marker or a plurality of discrete markers arranged at intervals one after the other in the circumferential direction, said markers being arranged on the rotor, and the at least one discrete marker varies along the axial direction in its extent in the circumferential direction, and/or different numbers of individual discrete markers are provided, one after the other in the circumferential direction, in different axial sections of the rotor.